Geomagnetic full vector fluctuation in Mexico over the last two centuries: Anomalous record between 1840 and 1940?

Study of the paleosecular variation of the Earth's Magnetic Field is an almost unique way to estimate the critical conditions at the core-mantle boundary. The continuous and quasi-periodic changes in the magnitude and directions (declination and inclination) could be detected from direct instrumental measurements or through the remanent magnetization of volcanic and sedimentary rocks. Burned archaeological artifacts are another reliable source of geomagnetic information. Besides the great efforts in Central and North America to retrieve the fine characteristics of the geomagnetic field during the last centuries, no homogeneous data distribution has still been achieved in Mexico and the surrounding areas. To improve the analysis of the geomagnetic full vector in Mexico, we compiled and updated available data for the last 200 years exclusively based on full geomagnetic vectors obtained from direct historical measurements, magnetic repeat stations, geomagnetic observatories and maritime exploratory campaigns. A relocation error procedure allowed the selection of 658 reliable data, discarding those belonging to the sites located in the most northern part of the analyzed area. The spectral analysis through the second derivatives reveals relatively fast fluctuations in both intensity and directions between 1890 and 1960. Moreover, a marked difference is observed between the Mexican record and global geomagnetic models between 1840 and 1940.